When working on molars and bicuspids following cavity preparation, a dentist usually uses a dental matrix band which is held tightly around a tooth using a dental matrix band retainer so that the filling will restore the natural contour of the tooth. The matrix band, as described in U.S. Pat. No. 2,466,830 to Tofflemire, is a metal strip which is usually folded diagonally intermediate of its length to produce two ends that are arranged in diverging relation with one another when the strip is flat. The matrix band is slipped around the single tooth with the free ends extending in parallel and approximate relation with one another from the central portion of the buccal aspect and the fold arranged on the lingual side of the molar or bicuspid. The matrix band is pressed down until it is disposed close to the gingival border. Once slipped around the tooth, the matrix band is tightened around the tooth by using a matrix band retainer.
Over the years, many matrix band retainers has been developed. Most recently, U.S. Pat. No. 5,055,045 to Dickie et al. discloses a disposable plastic matrix band retainer which can be unlocked from its tightened position over a single tooth within a mouth quadrant without releasing the matrix band from the retainer. Once removed, the entire plastic matrix band retainer must be discarded.
U.S. Pat. No. 4,915,627 to Hirdes discloses a matrix band retainer comprising a frame, a threaded rod screwingly displaced in the frame, a coulisse block arranged which holds a matrix band and a tightening spring which is held on the threaded rod and acts upon a quick tightening nut. Once place around a single tooth, the matrix band is tightened by tilting a quick tightening nut which slides the coulisse block in the longitudinal direction. Once this coarse adjustment is made, a fine adjustment is available by rotating a knob located at one end of the threaded rod.
U.S. Pat. No. 3,613,245 to Knight discloses a similar matrix band retainer in which the looped matrix band is passed through a recess in a movable block. Simplicity of design allows the movable block to be easily removed and replaced. Rotation of a sleeve moves the block and decreases the size of the looped matrix band around a single tooth.
U.S. Pat. Nos. 3,462,841 and 3,516,162 to Ainsworth describe a similar matrix band retainer in which the matrix band is provided with enlargements on the ends such which are pulled in order to tighten the matrix band around a single tooth. The matrix band retainer incorporates a tubular body which protects the lips against moving parts within the body.
U.S. Pat. Nos. 2,439,703 and 2,502,903 describe the Tofflemire Matrix Retainer which consists of a slidably mounted clamping block with a diagonally extending slot into which the ends of the looped matrix band are inserted. The ends of the matrix band are clamped against the block by rotating a knob. Once the matrix band is clamped in the block, the matrix band is looped around a single tooth. A wedge may be inserted between the tooth being treated and an adjacent tooth to allow inserting the matrix band around the tooth easier. The tightness of the matrix band around the single tooth can be adjusted by rotating a sleeve which retracts the block.
Although many matrix band retainers have been developed, they all have the same limitation in that only a single tooth may be treated at one time. In other words, if a dentist needs to restore two posterior teeth with Class II, III or IV carious lesions in the same quadrant of a patient's mouth, the dentist must treat each tooth separately by performing the same procedure on each tooth in a sequential manner. As a result, the amount of time required to restore both teeth is approximately twice the amount of time needed to treat a single tooth which diminishes the work productivity of the dentist and the comfort to the patient.